BSE in sheep bred for resistance to infection

摘要

Selective breeding for disease-resistant genotypes is being pursued as a means of eradicating scrapie (and bovine spongiform encephalopathy (BSE), if it is present) from sheep flocks. Here we show that the genotype associated with the highest resistance can still be infected with BSE by intracerebral inoculation. Although the relevance of this finding to sheep exposed to natural infection remains to be determined, it may have important implications for disease-eradication strategies. Susceptibility and resistance to transmissible spongiform encephalopathies (TSEs) in sheep is largely controlled by polymorphisms at codons 136, 154 and 171 of the gene that encodes prion protein (PrP). Representing the resulting alleles as the amino acids at these positions, susceptibility to scrapie is strongly associated with valine (V) at position 136 and/or glutamine (Q) at position 171, and susceptibility to experimental BSE is associated predominantly with the alanine-arginine-glutamine (ARQ) allele.